RIS-Assisted Sensing With Reciprocal Beam Pairs
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Solution Overview
Problem
Existing wireless communication systems face challenges in accurately performing sensing tasks due to limitations in configuring reconfigurable intelligent surfaces (RIS) for beam management, particularly in scenarios without a direct line of sight (LOS) channel to the target.
Innovation Solution
The configuration of reciprocal RIS beam pairs with controlled downlink (DL) and uplink (UL) angles of departure, enabling methods such as monostatic and bi-static sensing by reflecting and receiving sensing signals to enhance sensing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional beam management methods are used without RIS configuration, then system complexity remains low, but sensing accuracy and coverage deteriorate in non-LOS scenarios
Solution Approach 1:
A reconfigurable intelligent surface (RIS) is introduced as an intermediary component between the base station and the target object. The RIS comprises multiple programmable elements that can independently adjust their phase and amplitude characteristics to reflect and steer electromagnetic beams toward non-LOS targets, thereby enabling accurate sensing without direct line-of-sight connection.
Solution Approach 2:
The RIS elements are configured with dynamic reconfigurability, allowing the phase and amplitude of each element to be adjusted in real-time based on channel conditions and target position. This dynamic adaptation enables the system to optimize beamforming patterns for different sensing scenarios, maintaining high measurement precision while managing complexity through automated configuration.
2Reliability
If direct LOS channel is assumed for sensing, then system operation is simplified, but sensing coverage and reliability worsen in obstructed environments
Solution Approach 1:
The RIS serves as a relay intermediary that creates virtual line-of-sight paths by reflecting electromagnetic waves around obstacles. By programming the RIS elements to compensate for phase delays and amplitude variations introduced by non-LOS propagation, the system achieves reliable sensing in obstructed environments without requiring complex multi-path processing at the base station.
Solution Approach 2:
The system performs preliminary channel estimation and RIS configuration before actual sensing operations. The base station first establishes the RIS beam pairs by transmitting training signals and measuring reflections, then pre-configures the RIS element settings to optimize subsequent sensing performance. This preliminary setup simplifies real-time sensing operations while ensuring reliability.
3Area of stationary object
If reciprocal RIS beam pairs are configured with controlled DL and UL AoD, then sensing coverage is enhanced, but beam management complexity increases
Solution Approach 1:
The system configures reciprocal RIS beam pairs where the downlink and uplink beams have different angles of departure (AoD) optimized for their respective directions. The downlink beam AoD is optimized for transmitting sensing signals from the base station through the RIS to the target, while the uplink beam AoD is optimized for receiving reflected signals from the target through the RIS back to the base station. This asymmetric configuration expands sensing coverage by covering different spatial regions for transmission and reception.
Solution Approach 2:
The beam management process is segmented into distinct downlink and uplink configurations. Each RIS beam pair is independently optimized with specific AoD parameters for downlink transmission and uplink reception, allowing the system to manage complexity by treating each direction separately while achieving enhanced overall coverage through the combination of multiple beam pairs.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enhances sensing accuracy and coverage by leveraging RIS-assisted sensing techniques, overcoming LOS limitations and improving signal reflection and reception for precise target detection.
Implementation Method 1
receiving, at the BS, a first signal comprising a reflection of a sensing signal from a second BS off of a RIS
Data Source
AI summary
Disclosed are techniques for wireless sensing. In an aspect, a method for reconfigurable intelligent surface (RIS)-assisted sensing performed by a base station (BS) includes configuring one or more reciprocal RIS beam pairs for sensing, wherein each of the one or more reciprocal RIS beam pairs comprises a downlink (DL) beam having a DL angle of departure (DL AoD) from a RIS controlled by a first set of control voltages and an uplink (UL) beam having an UL AoD from the RIS controlled by a second set of control voltages. The BS may send, to the RIS, information identifying the one or more reciprocal RIS beam pairs. The BS may perform monostatic sensing using at least one of the one or more reciprocal RIS beam pairs.